The making of fiberglass reinforced plastic ("FRP") molds is a labor intensive and time-consuming process. Conventionally, a mold is made by hand laying-up multiple layers, one or two layers at a time, of a fiberglass mat impregnated with an unsaturated polyester, vinyl ester or epoxy resin. Each layer is hand rolled to remove air bubbles and allowed to cure for extended periods (e.g., four to 24 hours). This slow, methodical process is required to minimize volume shrinkage and the adverse affects of exothermic conditions that occur while the resin is polymerizing and reaching ultimate cure. Exemplary adverse affects include craze cracking, heat or thermal distortion, surface distortion, dimensional changes and internal stressing. Additionally, the molds, particularly large, long molds (e.g., molds for boat hulls) require post-construction stress processes to relieve warpage of the mold. Finally, the molds often have to be buffed and sanded over an extended period in order to obtain the desired surface finish, particularly when a smooth Class A finish article being molded is desired, such as in molding automobile body parts.
The resulting mold also must be resistant to heat distortion during use. Exothermic conditions of curing and the heat needed to cure some unsaturated polyester resins and other thermosetting resins tend to also cause heat distortion, warpage, craze cracking and the like. Conventional thinking in mold making is to use only those reactive polymers that have a high heat distortion temperature (e.g., distorts at temperatures above 120.degree. C.) so that the exothermic properties of reactive polymers during cure do not exceed the tooling resin heat distortion temperature. Thus, the selection of reactive polymers is limited to those that have heat distortion temperatures and T.sub.g 's above 100.degree. C. Resins having low heat distortion temperatures (e.g., below 90.degree. C.) and that cure at room temperature have heretofore not been used in the making of fiberglass reinforced molds.
Thus, there exists a need for a mold making process that produces a fiberglass reinforced plastic mold quickly, without the need for time-consuming multiple hand laying-up steps and extended time periods for curing, while minimizing volume shrinkage and the adverse affects of exothermic conditions during both the making and in the actual use of the fiberglass reinforced mold.